Scale.



E. G. POOL.

SCALE.

APPLIOATION FILED JULY so, 1910.

Patented Sept. 1, 1914.

Mfg/H655@ n UNTTED sTATns PATENT OFFICE.

ELMER C. POOL, 0F N-EW CASTLE, PENNSYLVANIA, ASSIGNOR TO TOLEDO SCALE COM- PANY, OF TOLEDO, OHIO, A CORPORATION 0F NEW JERSEY.

To alZ whom t may concern Be it known that I, ELMER C. Pool., a citizen of the United States, residing at New Castle, in the county of Lawrence and State of Pennsylvania, have invented certain new and useful Improvements in Scales, of which the following is a specification.

My invention relates more particularly to means for securing a correct reading of the scale in such devices as employ a movable chart of which the cylinder indicating or l computing scale is a well known example.

In devices of this character in order to secure a correct reading it must be taken off in each instance at a fixed ydelinitereading position. For this purpose the cylinder casing is provided with a vertical sight openingv opposite the reading position which is intended to be put on a level with the aver age observers eyes and a reading wire or line is mounted near the cylinder chart as nearly as may be in the same horizontal plane as the correct reading position. It is impractical, however, to place the reading line or wire very close to the movable chart but it must be placed at a slight distance therefrom. This would be immaterial if the'eye of the observer were always on a horizontal line with the reading line and the correct reading position. However', observers of different height necessarily read the scale from different altitudes above orl below` the horizontal plane of the reading position and the angle of the vision through the reading line being different, the latter is necessarily projeeted on the chart in positions above or below the correct reading position according as the eye of the observer is below or above the horizontal plane of the reading position. In order to correct for the position of the eye of the observer I have devised means whereby the reading line is projected upon the correct reading position no matter what the angle of observation of the reader.

I have shown my invention.v applied to a cylinder scale but it will be obvious that it is of much broader application and is available wherever a reading line and a relatively movable chart are used.

ln'the drawing Figure 1 shows a vertical section of a fragment of a cylinder' chart and casing with my invention applied thereto; Fig. 2 is a front elevation; and Fig. 8 a similar View with parts removed to better show the interior.

Specification of Letters Patent.

Application filed July 3Q, 1910.

Patented Sept. 1, 1914. seria1No.574,617. i

The chart 4 may be of any usual or suitable t'ype and is inclosed lin the customary casing 5 having an opening in the cylindrical wall thereof at a point opposite the correct reading position. Opposite to the reading position is mounted a sight tube 5 which consists substantially of a rectangular oblong boxing extending the length of the cylinder and open toward the cylinder and at its opposite end. Between the sight tube and the edges ofthe cylinder casing on either side of the reading position are mounted windows which may consist of panes of glass 6, (3 arranged at an angle as shown in Fig. l. The edges of the opening in the cylinder casing are provided with reinforcing strips 7, 7 which may be of cast metal, extend toward each other and are provided at their inner ends with inclinedy faces on which are mounted price scale strips 8, 8. These strips are arranged on either side of the reading position and within view through the sight tube. The outer end of the sight tube is closed by a pane of glass 9 upon which is drawn the reading line 10 extending horizontally across the pane. Of course a reading wire or similar means might be employed instead of the line upon the pane for the same purpose. lVithin the sightltube is arranged a pair of lenses 11, 12 each of which is plano-convex, the convex 'faces being arranged toward each other. Each of these lenses isof uniform cross section throughout its length and its curved surface is generated by a straight line moving in a parabola without changing its direction. The arrangement of lenses and reading line is such with reference to the movable chart that the reading line and the correct reading position on the chart are in respective conjugate focal lines of the lens system. It will be clear therefore that whatever the position of the observer-s eye, whether above or below the horizontal plane of the correct reading position the reading line will be projectedon the cylinder chart in the correct reading position.

While l have shown a system of-two lenses` it is clear that a greater number might be employed and the same result secured provided the parts were so arranged that the reading line and correct reading position were located substantially in the focal lines ofthe system. The lenses are held in place in the sight tube by suitable strips and spacers i3, le, l5, which may be secured by screws as shown. The sight tube and the framing for the Windows are shown as made orp sheet metal properly bent to shape though this precise construction is immaterial.

ln certain ot' the following claims l have referred to the lenses as cylindrical but it will he understood that they may be oit paraboloidal or other similar cross-section Without departing from my invention, the term cylindrical being used for convenience to include similar forms capable of obtaining the saine result.

lllhat l claim is:

1. ln a scale the combination of a movable chart, an element bearing a reading` line and lens system, the parts being' so related andv airanfgedthat an image ont the appropriate element of the chart is projected into coincidence with the reading line.

2. ln a scale provided with a movable reading chart, a casing inclosing the same but having a sight opening, an element bearine, a reading line and a. lens system intermediate the reading1 line and chart, the parts being so related and arranged that an image of the appropriate element of the chart is projected into coincidence with the reading line.

3. ln a scale, the combination of an elenient bearing a readingr line, a chart movable relative thereto, and a cylindrical lens system so arranged that the reading1 line and correct reading position on the chart respectively occupy the conjugate focal lines of the lens system.

4. ln a scale, the combination of an element bearing a readinir line, a chart movable relative thereto, and a pair of plano-convex cylindrical lenses constituting a system, the relation of the parts being such that the reading line and the correct reading; position on the chart of the scale occupy the conjugate focal lines of the lens system.

5. ln a scale, the combination of a chart, a casing therefor having a sight opening` opposite the reading position, ay reading`l tube covering the sight opening, and a Window adjacent thereto for admitting light to the reading position.

G. .ln a scale, the combination of a moveable chart, a casing therefor having,l a sight opening, a reading tube, an element hearingf a reading, line arranged across the tube, a lens system for projecting,T the reading line in correct reading position on the chart a Window adjacent the correct reading pd sition for admitting light thereto.

7. ln a scale, a movable chart, a casing surroundingl the saine haring an opening opposite the reading` position, a reading' tube, an element bearing a reading line mounted in the reading' tube, a cylindrical lens system also mounted in the reading tube, the arrangement being such that the reading line and the correct reading position on the chart are substantially in the conjugate focal lines of the lens system, and a price per unit scale adjacent the correct reading pcsitien and risible through the reading tubea .LVER C. FCL *w itnesses limon nn ll/l. Unna, Bnssm Mime. 

